1. Field of the Invention
The present invention relates to an actuating device having a high degree of freedom of movement.
2. Description of the Prior Art
In a prior art actuating device such as a linear pulse motor, as shown in FIGS. 1 and 2, a slider 101 is moved on scale teeth 103 by supplying a current i through a control signal line 102 connected to the slider 101. By repeating modes .circle.1 - .circle.4 of FIG. 1, magnetic fluxes of magnetic poles 1-4 are combined with magnetic fluxes of a permanent magnet PM so that a stable position between the slider 101 and the scale teeth 103 is sequentially shifted. In the mode .circle.1 of FIG. 1, a positive (+) current is supplied to a coil A and the magnetic flux is maximum at the pole 1 (the magnetic flux of the PM+ the magnetic flux of the coil A), and the pole 1 is the stable position. The magnetic flux at the pole 2 is zero (the magnetic flux of the PM-the magnetic flux of the coil A), and the magnetic forces at the poles 3 and 4 are balanced. In the mode .circle.2 , the positive (+) current is supplied to a coil B, and the magnetic forces at the poles 1 and 2 are balanced, the magnetic flux at the pole 3 is zero (the magnetic flux of the PM- the magnetic flux of the coil B) and the magnetic flux at the pole 4 is maximum. Thus, the pole 4 is the stable position. In the mode .circle.3 , a negative (-) current is supplied to the coil A, and the magnetic flux at the pole 1 is zero (the magnetic flux of the PM- the magnetic flux of the coil A), the magnetic flux at the pole 2 is maximum (the magnetic flux of the PM+ the magnetic flux of the coil A), and the magnetic forces at the poles 3 and 4 are balanced. Thus, the pole 2 is the stable position. In the mode .circle.4 , the negative (-) current is supplied to the coil B, and the magnetic flux at the pole 3 is maximum (the magnetic flux of the PM+ the magnetic flux of the coil B), the magnetic flux at the pole 4 is zero (the magnetic flux of the PM- the magnetic flux of the coil (B). Thus, the pole 3 is the stable position.
Thus, by supplying the currents to the coils A and B in the sequence of the modes .circle.1 , .circle.2 , .circle.3 and .circle.4 shown in FIGS. 1 and 2, the stable position is sequentially shifted in the sequence of the poles 1, 4, 2 and 3 and the slider 101 is moved relative to the scale teeth 103.
The stable position is shifted by P/4 per step, where P is a pitch of the scale teeth 103.
FIG. 3 illustrates a principle of a two-axis linear motor (plane motor) in which the principle of the linear pulse motor is extended to a two-dimensional plane. Projecting (e.g. square-shaped) scale teeth 303 are arranged in a matrix in x and y directions on a surface of a planar plate 301. A slider (302) (corresponding to the slider 101 of FIG. 1) which has signal lines (not shown) for the x and y directions and a plurality of magnetic poles (not shown) is arranged on the scale teeth 303 in a manner to allow smooth movement of the slider in the x and y directions so that the slider is directly moved in the x and y directions. In such an actuating device, a high degree of freedom of movement is not attained.